003-action-system.md

003 - Action System (Command Pattern)

Context

Creatures need to perform actions (Attacks, Spells, etc.) and resolve them against targets. We need a system that decouples the definition of an action from its execution and allows for complex resolution logic (dice rolls, stats comparison).

Decision

We decided to use a Command Pattern variation for Actions.

Key Interfaces

• IAction: Represents a potential action (e.g., "Longsword Attack"). It has an Execute(source, target) method.
• ICombatStats: Encapsulates combat stats like AC, Initiative, and Speed.
• ActionResult: A record returning the outcome (Success/Fail, Message, Damage).

Implementation

• AttackAction: A concrete implementation of IAction for weapon attacks.
  • Rolls d20 + AttackBonus vs Target AC.
  • Rolls Damage on hit.
  • Applies damage to Target via IHitPoints.TakeDamage.
• ActionType: Enum distinguishing Action, Bonus Action, Reaction, etc.

5e Rules Adherence

• Movement: Modeled as Speed in ICombatStats. Movement is a resource, not an Action type (though Dash is an Action).
• Attacks: Follow standard d20 + Mod vs AC rules.

Consequences

• Pros:
  • Extensible: New actions (Spells, Feats) can be added by implementing IAction.
  • Testable: Actions can be tested in isolation with mocked dice/creatures.
• Cons:
  • Complexity: Requires careful management of dependencies (DiceRoller) within actions.

Status

Accepted and Implemented.